The present invention relates to a one-way drive gear wheel assembly and, more particularly, to such a one-way gear wheel assembly in which the hub runs idle without producing much noise when the gear wheel is not in the driven status.
In order to save labor, a bicycle is equipped a one-way drive gear wheel, which is mounted on the rear wheel hub and coupled to the chain wheel by a chain. When the bicycle rider propels the pedals in clockwise direction, the one-way drive gear wheel is rotated clockwise, and the rear wheel hub is rotated with the one-way drive gear wheel. When the one-way drive gear wheel is not driven or rotated counter-clockwise, the rear wheel hub is free from the effect of the one-way drive gear wheel and keeps rotating clockwise due to inertia effect. FIG. 6 shows a one-way drive gear wheel assembly constructed according to the prior art for this purpose. This structure of one-way drive gear wheel assembly comprises a gear wheel (sprocket) A, a ratchet wheel B mounted in the inner diameter of the gear wheel A, a plurality of stop elements A1 mounted in the inner diameter of the gear wheel A, a plurality of pivots C1 respectively mounted in the inner diameter of the drive wheel A adjacent to the stop elements A1, a plurality of pawls C respectively pivoted to the pivots C1, and a plurality of torsional springs D respectively mounted on the pivot C1 and stopped between a part of the gear wheel A and the stop elements A1 to force the pawls C into engagement with the sloping teeth B1 of the ratchet wheel B. When rotating the gear wheel A counter-clockwise, the ratchet wheel B is rotated with the gear wheel A counter-clockwise. When stopping the gear wheel A, the ratchet wheel B keeps rotating counter-clockwise due to inertia effect. When rotating the gear wheel A clockwise, the pawls C are moved over the sloping teeth B1 of the ratchet wheel B without carrying the ratchet wheel B, i.e., the gear wheel A runs idle. However, because the pawls C are moved over the sloping teeth B1 of the ratchet wheel B during counter-clockwise rotation of the gear wheel A, much noise is produced.
It is one object of the present invention to provide a one-way drive gear wheel assembly, which produces less noise during its operation. It is another object of the present invention to provide a one-way drive gear wheel assembly, which produces less friction resistance during its operation. It is still another object of the present invention to provide a one-way drive gear wheel assembly, which automatically forces the hub away from the gear wheel for free rotation when the gear wheel is stopped. According to the present invention, the low-noise low-friction resistance one-way drive gear wheel assembly comprises a gear wheel, the gear wheel comprising an inner diameter, and a plurality of elongated recesses equiangularly spaced around the inner diameter and extended in radial direction, the elongated recesses each having a relatively wider front end, a relatively narrower rear end, and a neck on the middle between said relatively wider front end and the relatively narrower rear end; a hub inserted through the inner diameter of the gear wheel; a plurality of first rolling balls respectively moved in the elongated recesses of the gear wheel between the relatively narrower rear end and neck of each of the elongated recesses of the gear wheel and disposed in contact with the periphery of the hub, the rolling balls having a diameter greater than the width of the neck of each of the elongated recesses of the gear wheel; a plurality of ball racks respectively mounted in the relatively wider front end of each of the elongated recesses of the gear wheel and spaced from the periphery of the hub; a plurality of second rolling balls respectively mounted in the ball racks and peripherally disposed in contact with the periphery of the hub; and a plurality of spring members respectively mounted in the relatively wider front end of each of the elongated recesses of the gear wheel and adapted to support the ball racks and to force the ball racks and the second rolling balls toward the neck of each of the elongated recesses of the gear wheel. When the gear wheel is rotated clockwise, the first rolling balls are moved to the relatively narrower rear end of each of the elongated recesses of the gear wheel forced into engagement between the gear wheel and the hub, thereby causing the hub to be rotated clockwise with the gear wheel. When the gear wheel is stopped, the first rolling balls are forced out of the engagement position between the gear wheel and the hub, enabling the hub to be rotated clockwise relative to the gear wheel.